Train control



C. S. BUSHNELL Jan. 29, 1929.

TRAIN CONTROL Filed May 2, 1924 [a 5 INV NTO gawk/95y Patentedllan 29, 1929,

warren stares CHARLES S. BUSHNELL, OF ROCHESTER, NEVJ YORK, ASSIGNOR TO GENERAL RAIL- YVAY SIGNAL COMPANY, OF ROCHESTER, NEW YORK.

' TRAIN CONTROL.

Application filed May 2, 1924. Serial No. 710,536.

This invention relates to automatic train control systems, and more particularly to means for protecting a tra n when moving from a siding into a'block already occupied the train advances, providing a gradually decreasing permissive speed, the cam eventually assuming an ultimate or minimum speed position and remaining in that position to establish a continuing minimum speed limitv A system of this type, it will be noted, is predicated on the assumption that a train will ordinarily pass through a caution. block before it enters. a danger block; but in practical operation it may haps pen for some reason that a train will enter a danger block without having traveled over the distance required to run the cam down to its minimum speed position, with the result that the minimum speed limit will not be set up at the entrance to such danger block as it'should be. For instan "o, it often happens that a train, moving in a clear block, backs into a siding to allow another train in the rear thoreot to pass it, after which the train in question leaves such siding and follows said another train. In this case, it will be evident that the cam or other slow action device may not have assumed its ultimate and minimum speed position at] time the tl'llll lll question, enters the danger block in which the other train is moving; It will be noted that train control apparatus of this kind, initself does not aliord adequate protection in the case just mentioned, because only caution, speed restriction is imposed, whereas the train should be restrieted'to a'danger or minimum speed.

, In accordance with the present invention,

it is proposed to solve this problemby providing a danger speed restricting device which is immediately efi ective upon initia tion toimpose a minimum speed restriction and which is initiated it two conditions 0011- currently exist, these conditions being present when a train leaves siding and moves into a danger block, but not Veryoften at least, under ordinary operatingconditions encountered in practice. These conditions are (l) danger traltic conditionsmanifested on the vehicle by suitable means in com- ,municatlon withthe trackway ahead; (2) an' existing speed of less than a certain value, for instance such as that imposed in a danger block. More specifically, it is proposed in accordance with the" present invention to provide a suitable stick device which may only be picked up if traffioconditions ahead are clear, and which will only be dropped it both trafiic conditions aredangerous and the speed at which the train is moving is latenesless than a certain predetermined value, this stick device being used to iinpose-afdanger, speed restriction when 1t 1S 1n lts abnormal deenergizcd or active condition.

tic features oi the invention will in part be pointed out hereinafter and inpart be obthe accompanying drawing,

Other objects, purposes, and characterisin describingthe invention in detail, r'ef er'ence will be made to the a"companying drawing, in which a trackway having a side ing associated therewith has been shown, together with suitable trackway.equipment, and in which a railway vehicle, together with the Hoar-earl apparatusor control-I ling the same and embodying the present invention, has been conventionally shown.

' Although the present invention-in;its broad aspectis applicable to various types of train cor 01 systems, en'iploymgr either ation of a continuous inductive control continuous or intermittent control from the.

and recognized ,in the art, so that a sim- A plified and diagrammatic illustration, -together with a brief explanation, will suffice to make clear the applicability of his invention tosucha system, withoutillustratingv or describing in detail the continuous inductive control system.

Tmolcwoy flppamtus.-Reterring to the each blocl drawing, the present invention, although the block I and the adjacent ends of the two other blocks H and 3 having been shown. ince the various blocks are the same, like parts of each block have been designated by like reference characters having distinctive exponents. At the exit end of provided the usual track battery 3, connected across the rails in series with the secondary of a transformer 4, which secondary may serve as the 'usual series limiting resistance of the track circuit. Atthe entrance end to each block and across the rails is bridged a direct current track relay T. Although the present train control'system may be used in connection with railways having wayside signals of the color 1ight,'position light, or "semaphore'type, or

may be "applied to a system which does not include such wayside signals if suitable cab signals, which for convenience have not been shown,are provided, the train control systern has beenshown applied to trackway paratus including semaphore signals Z,

' which have been conventionally shown without illustrating their well known circuits and control devices. Underclear traffic conditions in each block 'as the, block I, the block, as H, next in the rear, in addition to the direct current supplied thereto, ash-eretofore explained, is supplied with alternating current from the transformer e. In the arrangement shown, a line transformer 5 has its primary winding connected to a suitable source'of alternating current, illustrated as atransmissionline P, and has its secondarywinding connected to the primary Wviiicling of the transformer i by a; circuit including the front contact 6 of the track relayT of the block next in advance.

In thefparticular arran ementshown, a "siding S. comprisingtrack rails 7 enters the main track in the block I hear the entrance thereof. The switch points for this siding Sare operated manually or by power in the usual manner by means which, for convenivence, has been omitted from the drawing. This siding S is provided with insulating fee joints 8 and is cross bonded in the usual manner, so asto' provide fouling point protection. o

It shouldbe noted that alternating current is present in the track rails of a block in advance of a train only if both the'por tlon of said block 1n advance of said train and the next block in advance are clear. This control of the alternatingcurrent in a 7 block is accomplished in two difilerentways.

In the first instance, no alternating current is present ahead of a train in a block when the next block 1n advance is occupled, be-, cause alternating current is cut off at the primary winding of the transformer i by the track relay of the block aheadyand in the second instance, even though alternating current may be applied to the track rails from the transformer 4 of a block in questicn,'suchcu-rrent is not able to reach a train in the block if that block is occupied by another train ahead, because said another train will shunt the alternating current away.

from the train in question, so that no alternating current may be detected by this following train. I

Car-carried appammaiis heretofore mentioned, a car-carried apparatus includes a two-position main car relay Mltwhich is controlled from the trackway. This relay MR has'been conventionally shownand is normally maintained energized by current induced in coils 11 and 12 disposed over the track rails in front of the train, illustratec by the axle 13 and wheelsl't. This induced current is amplified by'a suitable amplifying device A, shown diagrammatically,

which includes suitable thermionic or vacuum tube amplifiers, tuning devi es, and the like, well-known to those skilled. in the art of continuous inductive train control sys-J weights or'springs in theusual way to a deenergized position, and operates suitable contact fingers shown conventionally. In the type of system shown, the car relay MR has only two controlling positions, energized and deencrgized. V

I As heretofore mentioned, the present invention is particularly applicable to train control systems in which a delayed action device is used; and as shown the delayed action device is a distance element operated in accordance with the progress of the vehicle along the track, similar to the arrangement shown in the patent to Simmen, No, 1,150,- 309, dated August 17, 1915, and in the form also shown in. the application of V7. K. Howe, Ser. No. 38,132, filed July16,l915. Since this type of speedcontrol apparatus is described at great length in. this patent and pending application, a diagrammatic'il- 'lustration and a brief description of this having a mutilated gear 21 and a cam 22' keyed at opposite ends thereto. This shaft 20 is biased to the normal position shown by a spring 23.. Directly over the mutiliated gear 21 is disposed a worm 24 fixed to a tiltable shaft 25 which'is driven from the wheels of the vehicle through a suitable universal joint (not shown), so that this worm may be moved up and down freely without interfering with the driving ofthis shaft by said wheels. The shaft 25 is normally held in the raised position, so that the worm 24 is out of engagement with the mutiliated worm wheel '21, by a cam starter magnet CS, which is" energized through a front contact 26 of the main relay MR by a suitable source of energy which, for convenience, has been designated by the terminals B and C. It will be noted that deenergization of the cam starter magnet CS allows the shaft 25 and worm, 24to assume a lower position by reason of gravity or a suitable spring, so that the worm 24.

operatively engages the 'mutilitated worm wheel 21, and that continual rotation causes the cam 22 to be rotated until the worm 24 reaches the mutilated portion of the worm wheel 21. It will be noted that, the operative connection between the coil of the cam starter magnet CS and the shaft 25 comprises a core 27, having a forked end pivotally secured to a sleeve 28 rotatable on the shaft 25 The various positions assumed by the cam 22, as will more clearly appear hereinafter, determine different permissive; speed lll'lllLS at which the train may travel without incurring anautomatic brake application, and in practice the cam is shaped to set up speed limits at different points in a block'wh ch conform w1th the speeds of a brake performance curve taken on a track having a certain grade by a train of a cer-' tain class, so that the speed limits set up are ideal for certain standard or average conditions. These var ous posltions of the shaft 30 are determined by the arm 31,

pinned. to the shaft 30, which engages a grooved collar 32 of a centrlfugal speed-responsive device, or governor G. This gov-,

ernor G has been conventionally illustrated and is mounted on the shaft 33, also driven from the wheels of the vehicle, and includes centrifugal weights or fly balls 34 which tend to move outwardly by the action of centrifugal force and move the grooved col-, lar downwardly,- and a compression coil spring moved downwardly as-the speed of the train increases. To the shaft 30 is pinned another arm' 36 which has a. floating lever 37 connectedto the free end thereof,v the other end of this floating lever having aroller 38 hearing against the surface of the cam 22 by reason of the tension spring 39.

It is thus noted that the mid-point of the floating lever '37 responds both to the posi-j.

35 opposing the centrifugal action of these fiy balls, so that the collar 32 is tion of the cam 22 and 'the speed as mani-j fested by the speed-responsive device G.

All that is necessary to control the. train if.

the speed, determined by the speed-responsivedevice G, istoo high as'compared with the position the cam 22 assumes, is to cause an application of the brakes if this mid-point: 'of' the floating lever moves a" predetermined distance towardthe right. A contact for controlling a suitable brake control apparatus, when the mid-point of this floating lever assumes a predetermined'posi t1on, has been illustrated and comprises a movable contact 40 and a stationary contact 41, which contacts are normally held in contact with each other by means'of a roller 42 engaging a sector 43'o1'ierative1y connected to the mid-point of the floating lever 37 by the link 44, so that transverse movement of. the mid-point of the floating lever causes rocking of the sector 'about itspivotfi The sector 43 is provided with cut away por-ff tion and thereby allows the contact 40 to separate from the contact 41-, so that. these contactsare operated to break a circuit when the actual speed of the tram is in excess of" the permissive speed established by the cam The speed shaft 30,;in addition to: deter mining the position of the lower end ofrthe' to, is biased toward the-left, so that this' roller49 engages the edge .of the actuator 47, and the contact itself engages astation ary contact 50. 'Another movable Contact 51, is operatively connected to the contact 48 by .an insulatingstrip or link52, so that y the contacts 48 and til-move together in response to the position of the roller 49;

Adjacent the contact 51 is a stationary con tact-53 which. is normally out of engagement with the contact 51; The actuator is so shaped that the contacts4850 and 51-53 assume the position shown, ifthespeed of the train is greater than, say, 20 milesper hour, but assume the reversed position, so

that the contacts 48%50 are open and con.

tacts 51 and53 are closed, if the speedis' 7 less than this value. The purpose of these contacts will be more particularly pointed out in connection with the operation of'the system hereinafter. I I

-tis contemplated in accordance with the present invention to automatically apply the;

brakes in a'manner so that the engineer cannot prevent stoppage of the train as soon as the speed is excessive, as determined by theqcam 22. Since the present invention is not directed to any particularztype of brake applying apparatus, and: since any one of the various devlcesheretofore recog-,

nized for-this purpose may be employed in a system embodying the present invention, no particular type of brake applying neans has been shown in detail. It is assumed that such a brake applying device will be pneumatically operated, and an electro pneumatic valve EPV, which is electrically controlled, has been shown for this purpose.

Under normal clear trafiic conditions, the electro-pneuinatic valve EPV is :n'iaintained energized through a circuit which may be traced as 't'oll.ows:beginning at terminal B of a suitable source of energy, wire 56, cam-governor contacts 40 and 41, controlled by the sector 43, wires 57 and 58., front contact 59 of a suitable stick relay SR, more particularly described hereinafter, wires 60 and 61, winding of the EPV, wire 62, back to a common return wireC, connected to the other terminal of said source of energy. It is thus noted that the device EPV assumes its deenergized position as soon as struction,

and includes two separate windings, the

contacts 40 41 open as far as the apparatus thus far described is concerned. It will, of course, be noted that a certain distance of travel is necessary after the main relay MR has been deenergized, before the cam 22 assumesits ultimate position (the position at which the Worm 24, reaches the mutilated portion ofthe worm wheel 21) and the minimum orlow speed-restriction is imposed. This feature in delaying the time at which the ultimate speed restriction takes place is characteristic of tlie'systen'i shown in the patent and patent application respectively referred to heretofore. In accordance with the present invention, as heretofore mentioned, it is proposed tohave this minimum speed restriction, assumed to be 20 miles per hour, imposed instantly under predetermined concurrent conditions of the main relay MR and the speed of the "train; and the low speed stick relay SR, together with the contacts controlled by the cam 47, have been provided for this purpose. v

T1118 stick relay SR, of the usual conhas been shown conventionally,

upper winding of which is energized, when the ma n relay MB is in its energized position through the contact 66 of this relay, loy a circuit readily traced in the drawing. With the stack relay SR once energized, its frontcontact 67 is closed, and if the speed of the train is above 20iniles per hour, a stick circuit including the lower winding 68, the front contact '67, and the speed contacts 4 85O, is closed. It will thus be noted that with this relay SR ener gized, by its stick circuit, it will assume its deenergized position if both the relay MB is deen'ergized and the speed of the train is'less than 20 miles per hour. with the stick relay SR de-energi7ed, the front contact speed oi the train is at that time above 20 miles per hour, regardless of the'position of the cain22. Consequently, it the train stops or runs at a speed less than the minimum under caution ordanger traiiic condi ti'ons, it can not thereafter run fasterthan the minimum speed until the car relay MR has been re-energized from the trackway and acts to pick up the low speed relaySR.

Operatioa.llndcr ordinary trafiic conditions, as soon as the trainenters a caution block, the relay MR drops, because the alternating current has been cutoff of such block by the track relay oi. the block ahead, as is obvious from the'drawing. As the train moves through such a' caution block, the cam 22 turns and gradually restricts the porn issive speed of the train, bringing the train to a minimum speedof, say, 20 miles per hour before it reaches the danger block.

As the train moves into the danger block this relay MR remains in its deenergiz'ed position, because the alternating current, if on the track rails, is shunted by the train ahead. It should be noted that, traffic conditions clear up while a train is travel ing in a. caution block, the relay MR is immediately energized, regardless of the position of the train in the block, so that the train may again proceed restricted only to a maximum speed limit, setup by the cam 22 inits restored position.

yLet us assume that a train, equipped with the apparatus described, is moving iromleft to right through theblocks H and I, with another train following close behind, and that the first train by schedule, or train order, is required to take the siding S shown,

, so as to allow the other" train to move ahead.

As the first train ahead backs into the siding, the cam 22 will remain in its normal position until the receiving coils 11 l2 come back ofthe insulating joint's'S, this lU'n on the assumption that trafiic conditions.

ahead are clear. back of the fouling point, themain relay MBand the cam starter magnet CS are de-,

energized so as to start the cam 22 in rotation. However the train, although it has backed far enough into the siding to allow the othertrainto pass, has not moved the cam 22 appreciably from its normal position. As soon as the other train has passed As soon as the train gets 'mum speed restriction, since it would then be traveling in a danger or occupied block. As far as the cam 22 and its control from the trackway are concerned, however, the

.train coming from the siding S might be permitted to run at a speed much higher than the minimum speed, depending upon how far the cam 22 had been driven toward its ultimate or minimum speed position by the time the train passed from the siding on to the main track. In the particular case assumed, with the train backing into the siding under a clear signal, it can be seen that the cam 22 would be substantially in its normal maximum speed position when the train came out on to the main track, permitting the train, as far as the cam is concerned, to accelerate to'a comparatively high speed. If the train had entered the siding S from the opposite end, the cam 22 would i have been partly run down to some intermediate speed position while the train moved along the siding, inasmuch as the car relay MR would be deenergized and connect the cam to the car wheels while the train was running on the siding which would not be supplied with. train control current. v

The low speed relay SR, however, and its manner of control provides for such con- .t1ngenc1es as above GXPltLHlQCl." Assume that the train pulls out of the siding S with the cam- 22 in its maximum speed position, or at least at some relatively high speed position. While this train is on the siding, back of the fouling'point, the car relay MB is de energized, breaking the pick-up circuit for the relay SR. Also, since the train on the siding is at a standstill, the contacts l850 are opened, breaking the stick circuit of the.

low speed relay SR. Consequently, both energizing circuits for the relay SR are nterrupted; and irrespectlve of the position of the cam 22, the minimum speed limit is enforced by contacts5l 53 as the train pulls out from the siding. It the block I is a danger block, by reason of the passage of the other train by said siding in the normal direction of traiiic, the car relay MR on the train in questionnow moving off of the siding remains deenergized, because the train control current in the portion of the block I between the two trains, is shunted out by the other train ahead. The low speed relay SR remains deenergized and the minimum speed limitremains inforce so long as the train ahead stays in the block I. In the two-position. type of system shown, the low speed limit also continues in force until the block I becomesra clear block, or until the following train is able to pick up train control current. As soon as the block in which the train is running becomes clear and the car relay MR picks up, the low speed relay SR is reenergize'd by. closure ofits pick-up circuit; and the train .may thereafter proceed at maximum speed, the cam 22 being restored to the normal position at the same time. From this explanation it willbe under-' stood that, whenever acar equipped with apparatus according to the invention stops or slows down below a predetermined low:

speed limit while the main car relay MB is deenergized, the minimum speed. limit is thus rendered effective, and the train-cam, not thereafter proceed faster than this minimum speed limit until the carrelay MR has been again energized. Such an arrangement provides full protection for trains coming off "of sidings into occupied blocks, and does not materially interfere with train movement under regular operatingcondi tions. In the particular two-position type of system disclosed, the samecontrol, namely deenergization of the car relay, exists in a caution block as in a danger block; and for this reason a minimum speed limit is enforced under some circumstances where not essential for safety. For example, as a train enters a caution block below the minimum speed, it is held down to this minimum-speed until the block clears. This is not true of a system where a distinctive control is pro- .vided for a danger block different from a caution block, the relay SR in such a case not being deenergized, although in a caution block the speed is low or the train has. stopped, and is deenergized only in adan ger block. It will be obvious that it is proper to have the low speed relay SR deenergized in a danger, block, 'sincethefmin imum speed limit should be enforced; The invention is applicable to the well known three-position type of continuous inductive control system, employing a.three position car relay. It is also evident that the invention is not restricted to acontinuous inductive control system of'anytype, but in its broad aspect is applicable to any type ioo of system employing a speed-responsivede- 5 viceon the car, with a delayed action device tor setting up the minimum speed. restrictained from the trackway under unfavorable conditions; It should also be undertion,irresp ective of how tllGuCOlltIOl isob stood that a thoroughly complete system 7 meeting all practical operating -requirements would inoludeother devices and features not herein disclosed. For example,"

incorporated with the particular means of this invention without altering the nature oftheinvention or itsutility and advantages. It should also be understood that various changes, additions and modifications may be made in the particular construction shown and described, without departing from the nature or scope of the invention or thetbroad concept of means underlying the same.

lVhatI claim is 1. In a train control system of the continuous inductive type in which gradually reducing permissive speed limits are set up by suitable mechanism when adverse traffic conditions are set up as manifested by the absence of current normally flowing in the track rails aheadof the train, the combination with brake 'control means for effect ing a: brake application if the actual speed of the train exceeds the permissive speed set up by said mechanism, of means for at ting up a low permissive speed limit abruptly which the vehicle cannot exceed without incurring a brake application, said last menmanifested, said last'nientioncd means if tioned 'means being rendered active if dangerous tratiic conditions are manifested and the speed of the train is below a predetermined value simultaneously.

2. In a train control system of the contin-' uous inductive type in which gradually reducing permissive speed limits are set up by suitable mechanism when adverse trafiic conditions are set up as manifested by the absence of current normally flowing in the track rails ahead of the train, the combination with brake control means for effecting a brake application if the actual speed of the train exceeds the permissive speed set up by said mechanism, of means rendered active to set up a low permissive speed limit which the vehicle cannot exceed without incurringa brakeapplication if the speed of the vehicle isless than a predetermined value while dangerous traflic conditions are once active remaining active until iavorable traffic conditions are again manifested.

Car-carried apparatus for automatic train control systemsof the speed control type comprising, a speed restricting oevice normally in its inactive condition which if momentarily actuated assumes its active condition, and means for actuating said device if-the speed at which the train is traveling is-less than a certain predetermined value and trafiic conditions, as manifested by influences transmitted by apparatus for continually transmitting influences from the trackway to a suitable car-carried influence receiving device, are dangerous.

4. An automatic train control system comprising, a delayed action permissive speed device which is delayed in accordance -with the progress of the vehicle along the control means on a railway vehicle for indicating the conditions of trafilc ahead, means partly on the vehicle and partly along the trackway and acting through an intervening air-gapfor controlling said .control means, a delayed action device governed by said control means initiated; when said control means is deenergized and which sets up a minimum permissive speed limit when it,

reaches its ultimate condition, an unretardcd device for setting up a minimum permissive speed limit whenboth said control de vice is in its deenergized condition and the speed of the vehicle is below a certain value, and means for causing an automatic brake application if the speed of the vehicle is higher than the permissive speed set up by either of said devices. Y

6. An automatic train control system com'- prising, a brake setting device, a device responsive to the actual speed of the vehicle,

permissive speed mechanism, and means for rendering said permissive speed mechanism active to set up a low speed limit only when trahic conditions ahead aredangerous and the speed as manifested bysaid speed responsive device is below a certain value, and

lay havinga stick circuit including its own contactand a contact governed by said speed responsive device which is open 'when the speed of the vehicle 1s below a certain value in series, and means for restricting the speed of the train if said stick relay is deenergized, or sand control relay is deenergized.-

8. Car-carried apparatus for train control systems comprising, a speed responsive device, a stick relay, a circuit for energizing said relay including a front contact of said relay and a contact governed by said so 5. In an automatic train control system, the combination of a normally energized ",ll. Car equipment for train control sysa'permissive speed device controlled by said relay and effective when said relay is deenergized, a brake setting device, and means for actuating said brake setting device if the speed of the train exceeds the permis-' sive speed set up by said permissive speed device.

9. Car-carried apparatus for train control systems comprising, a speed responsive device, a stick relay, a circuit for energizing said relay including a front contact of said relay and a contact governed by said speed responsive device and open whenthe' speed of the train is below a certain value, a control rela a permissive speed mechanism in-' eluding a permissive speed cam which sets up gradually decreasing speed limits as the train proceeds through a block of trackway when initiated, a brake setting device, means for rendering said permissive speed mecha nism active to set up permissive speed limits when either of said relays are deenergized, and means for actuating said brake setting device if the speed as manifested by said speed responsive device exceeds the permissive speed set up by said mechanism.

10. In a train control system, car appara tus comprising, a speed-responsive device driven from the car wheels, a movable ele ment determining by-its position the limiting permissive speed for the car and adapted to be connected to the car wheels,brake applying means operated'whenever the actual speed of the car exceedsits permissive speed represented by the position of said movable element, a low speed device ior establishing a minimum speed limitindependently of the position of said movable element, and means controlled from the trackway for rendering said low speed device effective only when I simultaneously the speed 01 the car is below a predetermined minimum and unsafetratdc conditions ahead exist.

terns adapted to protect train move rent from sidings on to main tracks con'iprising, in combination with speed control apparatus for enforcing predetermined speed limits under caution anddanger trafiic conditions after an interval of delay, o:t a low speed device capable of enforcing a minimum speed limit independently i said apparatus, and automatic 'n'ieans for re idering said low speed device effective on a carrunning from a siding into a danger block.

12. Car equipment for train control systems comprising, a control relay governed from the trackway and assuming a predetermined danger condition in an occupied or danger block, a speed-responsive device driven from the car wheels, a low speed stick relay effective when deenergized to establish in cooperation with said speed-responsive deice at minimum speed limit which the car cannot exceed without an automatic brake applieatiom'apick-up circuit for said low speed relay interrupted when'the control relay assumes said' danger condition, and a stick circuit for said low speed relay including contacts operated by the speed-responsive device and opened at all speeds above said minimum speed. i

13. Car apparatus t'ain control systems comprising, a speed-responsive device driven from the car wheel s, minimum speed contacts operated by said device and opened at all speeds above a predetermined minimum, a? low speed stick relay, a brake setting appliance, a normallyclosed circuit including said appliance and having two branches in multiple, one-of said multiple branches including said minimum speed contacts and the other branch including a 1"ront contactof said low speed relay, a controlrelay governed from the trackway and deenergized stick circuit for said low speed relay con trol ed by the'speed responsive device andopened whenever the speed otthe car is above a predetermined low speed.

14. In a train control system of the type employing a permissive speed device changeable in accordance with the distance traveled by the car, the combination with a car relay controlled from the trackway and governing the permissive speed device, a slow speed r'elay adaptedwhen deenergized to enforce in dependentlyof said permissive speed device a minimum speedlimit which the car cannot exceed without an automatic brake applica tion, and automatic'ineans for deenergizing the low speed relay effective only if thecar have a mined. ,minimum' speed in territory where danger tratfic conditions are maniiestedby v the deenergized condition of saidcar relay.

15. In an automatic train control system of: the continuous inductive type, the combination with. a main relay on the vehicle which assumes an energized condition in re-- sponse to current flowing in the track rails ahead of the vehicle under favorable traffic speed between zero and a predeterice;

con'ditions ahead, speed contacts closed it tie speed of the vehicle is below a predetermined value, a brake control device normally energized through a circuit mcluding said speed contactsa stick relay having a pickup circuit closed it said main relay is i'n an energized condition,

a stick circuit for said stick relay including contacts closed onlyi'f i the speed of the vehicle is above a certain value, and contacts on said stick relay closed it said stick relay is energized for shunting said speed contacts, whereby said stick relay is deenergized to enforce said predetermined 1 v speed value if the train travels at less than said certain speed while said main relay is deenergized. '7

16. In an automatic train control system of the continuous inductive type, the combination with a main relay which assumes an energized condition in response to the flow of current'in the track rails ahead of the train, a permissive speed device normally maintained inactive and which if rendered active, sets up gradually decrea ingspeed limits, another pernissive speed an energized condition in response to the flow of current in the track rails ahead of the train, a permissive speed device normally maintained inactive and which if rendered active sets up gradually decreasing speed limits, another permissive speed device for abruptly setting up a low speed limit, a device for indicating the actual speed of the train, a brake control device rendered active if the actual speed exceeds the permissive speed limit set up by either of said permissive speed devices, and means for rendering said another permissive speed deviceactive it the said main relay is deenergized and the speed of the train is less than a certain value concurrently. r

18. In an automatictrain control system of the continuous inductive type, the combination with a main relay which assumes an energized condition under favorable traffic conditions in response to the flow of cur rent in the track rails ahead of the train, a permissive speed device normally maintained inactive by said main relay and which if rendered active sets up gradually decreasing speed limits, another permissive speed device for abruptly setting up a low speed limit a device for indicating the actual speed of the train, a brake control device train control systems of the speed control type, comprising a speed limiting de vice normally in inactive condition means for actuating the device on decrease of train speed below a predetermined value, and means causing said actuation of the device to be effective to limit train speed only provided traiiic conditions, as manifested by apparatus on the car, are not clear.

20. Car-carried apparatus for automatic train control systems of the speed control type, comprising, a speed limiting device normally in inactive condition, means for actuating the device on decrease or train speed below predetermined value, and means responsive to trafiic conditions for causing said actuation of the device to render such device effective to limit the speed of the train.

21. Car-carried apparatus for automatictrain control systems of the speed. control type, comprising, a speed limiting device normally in inactive condition, means for actuating the device'on decrease or train speed below a predetermined value, and means vresponsive to trafi ic conditions for causing said actuation of the device to render such device effective to limit the speed of thet are not clear.

In testimony whereof I hereby afiix my signature.

CHARLES s. BUSHNELL.

rain only if trafiic conditions 

